The invention relates to an increment charge for a fin-stabilized mortar projectile, the increment charge being provided with a substantially centrally located space for a tail shaft of the projectile to allow the increment charge to be mounted around the tail shaft, and with a mounting opening extending from the space to the edge of the increment charge, the opening being smaller in width than the tail shaft.
Fin-stabilized mortar projectiles typically have a tail shaft extending from the cartridge containing the actual explosive, the tail shaft being provided with guiding fins fixed thereto. There are typically four or more guiding fins, although their number may vary.
Inside the mortar tail shaft there is the usual propellant charge, which ignites upon firing and provides the projectile with a muzzle velocity of a certain magnitude, thus making the projectile fly in a predetermined manner.
Upon firing, the flight distance of these fin-stabilized mortar projectiles and thus their range can be controlled with different kinds of increment charges placed around the tail shaft of the projectile, the burning of the charges in the mortar barrel supplying added propulsion force to the projectile. By using increment charges of different type and different burning properties, it is possible to control the desired flight distance.
In prior art solutions increment charges are mostly round in shape so that they fit into a mortar barrel. Moreover, the increment charges have a mounting opening on one side to allow the tail shaft of the projectile to be pushed into a centrally located space of the increment charge the shape of which substantially corresponds to that of the tail shaft.
A problem with prior art increment charges is that they cannot be used in solutions in which the projectiles are kept in a separate ammunition cassette or holder and fed with a mechanical feeding device into the mortar barrel. The reason for this is that due to the mass of the increment charges, vibration causes them to set into a position in which their mounting opening faces upward and thus the increments may come off and drop. The possibility that an increment charge may come off is such a major risk factor in the handling of this type of ammunition that it cannot be allowed. Further, the increment charges are in different positions and therefore burn unevenly in the barrel, which may cause harmfully great variations also in the trajectories of the projectiles.